1. Field
The present invention relates to vacuum generators of the type in which a motive fluid flowing through an ejector pump creates a vacuum. More particularly the invention relates to valve means for controlling the flow of motive fluid in such a vacuum generator.
2. Prior Art
It is known to produce a vacuum by means of a motive fluid flowing through an ejector pump and to control the flow of motive fluid by means of valve which may be operable in response to a condition. For example, the vacuum condition produced by the ejector pump may be applied to an expansible chamber valve operator for controlling movement of a valve which in turn control the flow of motive fluid, Such devices tend to reach a stable operating condition in which the vacuum produced by the ejector pump holds the control valve in a partially open condition which permits sufficient flow of motive fluid to maintain the vacuum condition. Where motive fluid flows through a partially open valve, a portion of the available energy of the motive fluid is lost in overcoming flow resistance in the valve whereas it would be desirable to make full use of the available energy of the motive fluid. To this end it has been suggested to provide a valve operator means which moves the control valve between open and closed positions in order to reduce the losses arising from flow through the valve. For example, it has been suggested to provide a lost motion valve operator means for this purpose. Such devices are often complicated in structural organization and occupy considerable space. As a result, improvements in means for controlling the flow of motive fluid are desirable, particularly improvements which would result in a simpler more compact structural organization.